Method of preparing tubular artificial textile threads



Patented Nov. 15, 1938 UNITED STATES METHOD OF PREPARING TUBULAR ARTI-FICIAL TEXTILE THREADS Ren Picard, Lyon, and Ren Fays, Villcurbanne,France, assignors to Societe Alsa in Basle, a

corporation of Switzerland No Drawing. Application May 21, 1935, SerialNo. 22,518. In France May 25, 1934 '7 Claims.

This invention relates to the manufacture of artificial threads and moreparticularly to a process of producing artificial textile threads inwhich each filament is less than 2 deniers and also is 5 tubular, i. e.,has a continuous canal.

The regular production of an artificial silk or thread from viscose andof the type wherein each filament is provided with a continuous canalpresents, as will be understood, very great difliculties, even whendealing with filaments of an ordinary denier, i. e., of at least 2deniers. Prior to this invention, the production of a hollow filamenthaving a continuous canal and a denier less than 2 was consideredimpossible.

The present invention relates to the manufacture of an artificialviscose silk in which each filament is provided with a continuous canaland is of a denier lower than 2 and, in an accessory way, to varying ormodifying the feel of the product 0 thus obtained.

In copending application filed May2l, 1935, Serial No. 22,517, there isdisclosed a process of producing from viscose an artificial silk orthread wherein each of the filaments is tubular. If the filament denieris to be smaller than 2, then the process described in the copendingapplication must be supplemented by the instant invention, whichcontemplates the utilization of a spinning bath, the concentration ofwhich depends on filament denier desired. Specifically, the higher theconcentration of the bath, the smaller will be the filament produced.

In other words, we have found that by utilizing the principles of theprocess described in the oopending application, previously referred to,in

conjunction with a spinning bath of higher concentration than set forthin said application, we can produce threads of the same filament count,

each of the filaments, however, being of a denier less than 2.

British Patent No. 163,817, of February 27, 1920, which was filed beforethe invention of artificial threads with tubular filaments had beenmade, laid down in principle that the higher the acid concentrationemployed in the coagulating bath, the finer will be the filamentsproduced, and that the proportion of acid which is necessary withvarious thread sizes has been found to be approximately inverselyproportional to the square root of the thread size. Related patentsmention the possibility of replacing in this general formula a portionof the sulphuric acid by a suitable proportion of ammonium sulphate.

, On the other hand, the British patent specification No. 255,527 showsin a diagram the zones in which the concentration of the spinning bathshould remain a function of the degree of ripening of the viscose, forthe special case of a thread having tubular fibers of a beautifulbrilliancy. The concentration is expressed in this specification by thespecific gravity of the bath, or for a given content of sulphuric acid,bythe quantity of sodium sulphate which must be dissolved therein. Sincethe specification contains no reference to the titer of the elementaryfiber, however,it is only logical to conclude that its subject matterrelates to an elementary titer of more than 2 deniers, which was themost usual custom at that period.

The principle of the British patent specification No. 163,817 and theindications of the British patent specification No. 255,527 are nolonger applicable when it is a matter of obtaining a thread havingtubular fibers of a titer less than 2 deniers.

We have found that in this case the acidity of the bath should beincreased but in a proportion other than that fixed by the Britishpatent specification No. 163,817, and that the essential factor is theconcentration of the bath and not its acidity. By concentration, we meanthe weight of dissolved matter per liter, including the acid. Accordingto our invention, the concentrations indicated in the British patentspecification No. 255,527 being considered as applied to a thread havingtubular fibers of 2 deniers, the said concentrations of sulphuric acidand sodium sulphate are to be increased by 20% at least, and preferablyby between 25% and 30%, the saturation point being the sole limit, whenthe titer of the elementary fiber is 1 denier. The increase for thetiters included between 1 and 2 deniers will be obtained by simpleinterpolation. It is evident that in all these cases, the ratio of thesulphuric acid to the dissolved sulphates remains constant, 1. e.,approximately 1:15. This rule may, in this case, be extended to thefilament of a half denier, although in practice it is already verydifficult to go below one denier, in View of the fact that a filament ofthis titer represents a continuous tube of 9,000 meters in length andweighing only 1 gram.

In accordance with the principles of this invention, a viscose solutionof the type which is employed in the manufacture of hollow filaments isspun into a spinning bath, hereafter more fully described. Thecoagulated and regenerated cellulose thread is then given a bath travelof not exceeding and preferably less than 25 centimeters. Afterwithdrawal from the spinning bath the thread is given a travel in air ofnot less than centimeters to ensure substantially complete fixationbefore engaging the delivery roller. The thread is then wound up in anysuitable manner as in a centrifugal spinning bucket.

It is to be noted that during the bath travel it is of advantage if thethread does not engage with any devices which impede the free travel ofthe thread. If the thread is to be stretched, this is preferablyeffected by suitable devices imposing the desired tension on the threadbetween the spinning bath and the delivery roller or beyond the latter.

The spinning bath contains sulphuric acid, sodium sulphate, andpreferably also zinc sulphate. The concentration of the bath dependsupon the filament-denier desired, 1. e. the higher the concentration ofthe bath, the smaller will be the filament produced. When afilament-denier of, for example, 1 is desired, the concentration of thebath is at least approximately 20% and preferably approximately 25% to30% higher than the concentration of the bath employed in the productionof filaments having a denier of 2. The bath concentration indicated inBritish patent specification No. 255,527 is considered as applied to athread having tubular fibers of 2 deniers. The concentration of the bathwhich is to be used in the production of filaments having a denier otherthan 1 and less than 2 can be secured by interpolation from theconcentrations herein given. For example, when a filament of 1.5 denieris desired, this can be secured by increasing the sodiumsulphate-sulphuric acid concentration approximately 13.8%. In all casesthe ratio of approximately 1 part of sulphuric acid to approximately 1.5parts of sodium sulphate is maintained.

By way of illustration, comparative examples are given merely toindicate the results which the instant process renders it possible toobtain, and without limiting the invention thereto. To a viscosesolution containing 7.3% cellulose and 4% caustic soda, sufiicientsodium carbonate is added to increase the total alkalinity to 7%. Theviscose solution is then ripened for 73 hours at 13C. and thereafterspun. to produce 100 denier-100 filament threads, into one of thefollowing aqueous bathsl Grams per liter a. Sulphuric acid 140.0 Sodiumsulphate 220.0 Zinc sulphate 2.5

b. Sulphuric acid 180.0 Sodium sulphate 280.0

Zinc sulphate 2.5

In each instance, the thread is given a bath travel of 20 centimeters.Also, in each case the thread, on leaving the spinning bath, travelscentimeters in the air before arriving at the delivery roller whichdelivers it at a speed of 60 meters into a centrifugal pot rotating at5,000 revolutions per minute.

When bath a was used, spinning was difiicult and each of the filamentswas not tubular. On the other hand, when bath 5" was employed, there wasno difiiculty in spinning and each of the filaments was tubular.

Another illustrative example of the instant invention comprises spinninga viscose solution of the type previously mentioned in the followingbath to produce a 100 denier-66 filament thread:

Grams per liter Sulphuric acid 160.0 Sodium sulphate 250.0 Zinc sulphate2.5

ditlOl'lS.

The bath travel, travel in air, winding, etc. are the same as in theprevious example.

In the example next preceding, no spinning difiiculties were encounteredand each of the filaments was tubular.

It is to be understood that the invention is not restricted to theforegoing examples. The examples have been set forth to permitcomparison of the results secured under three different con- It will beseen that, on this basis, assuming that the titer of the filament is 2deniers, as stated hereinbefore, by an increase in the concentration(sulphuric acid and sodium sulphate) of 27.6% a diminution of the titerby 1 denier is obtained, while an increase of 13.8% secures a diminutionof half a denier.

Using the concentration of Example 1 of British Patent 255,527 as theprior art bath, the following table gives the concentrations at thevarious percentage increases:

13.8% approximately 424 grams per liter 20.0% "approximately 448 gramsper liter 25.0% appro-ximately 466 grams per liter 27.6% approximately475 grams per liter 30.0% approximately 492 grams per liter Theseexamples clearly show the necessity of adding a new factor to that whichis indicated by the British Patent No. 163,817.

The threads obtained according to the present invention arecharacterized by an extraordinary suppleness, feel and curl. Theyprovide noncreasing fabrics. They have a very particular interest whenthey are obtained in the form of slivers intended to be cut up intolengths to constitute artificial schappe, the said slivers beingpreferably obtained on a continuous frame in which the sliver is spunand undergoes all the subsequent treatments as far as final drying.Thus, it is readily possible to produce slivers of 100,000 deniershaving fibers or" at most 1 denier, all provided with a continuouscentral channel. This spun material, having a Wooly appearance which hasnever before been attained, lends itself to numerous uses in fields intowhich artificia. silk has only rarely penetrated.

If instead of maintaining the ratio of the sulphuric acid to the sodiumsulphate at the value given by British patent specification No. 255,527,the quantity of sodium sulphate which corresponds thereto is caused tovary slightly, for example, 20 grams per liter more or less, the feel ofthe thread is modified. Starting from the concentration giving averagefeel, if the proportion is increased, the softness diminishes and thecurl increases; if it is lower, the converse takes place.

Since it is obvious that various changes and modifications may be madein the above description without departing from the nature or spiritthereof, this invention is not restricted thereto except as set forth inthe appended claims.

We claim:

1. Artificial threads composed of a plurality of tubular regeneratedcellulose filaments, each of said filaments being tubular throughout itslength and of a denier less than 2.

2. Artificial threads composed of a plurality of tubular regeneratedcellulose filaments, each of said filaments being tubular throughout itslength and of a denier of l.

3. Artificial threads composed of a plurality of tubular regeneratedcellulose filaments, each of said filaments being tubular throughout itslength and of a denier of 1.5.

4. In a process of producing threads composed of filaments, each ofwhich is tubular throughout its length and has a denier less than 2, thesteps which comprise spinning a viscose solution capable of producinghollow filaments into a bath containing sulphuric acid and sodiumsulphate in the ratio of approximately 1 part of sulphuric acid to 1.5parts of sodium sulphate, the total quantity ofboth the said sulphuricacid and the said sodium sulphate being in excess of approximately 373grams per liter, causing the thread to travel in said bath for adistance not in excess of centimeters, withdrawing the thread from saidbath and causing it to travel in the air for a distance of not less than150 centimeters.

5. In a process of producing threads composed of filaments, each ofwhich is tubular throughout its length and has a denier less than 2, thesteps which comprise spinning a viscose solution capable of producinghollow filaments into a bath containing sulphuric acid and sodiumsulphate in the ratio of approximately 1 part of sulphuric acid to 1.5parts of sodium sulphate, the total quantity of both the said sulphuricacid and the sodium sulphate being from approximately 410 to 492 gramsper liter, causing the thread to travel in said bath for a distance notin excess or 25 centimeters, withdrawing the thread from said bath andcausing it to travel in the air for a distance of not less than 150centimeters.

6. In a process of producing threads composed of filaments, each ofwhich is tubular throughout its length and has a denier less than 2, thestep which comprises spinning a viscose solution capable of producinghollow filaments into a bath containing the following ingredients inapproximately the following proportions:

Grams per liter Sulphuric acid 180.0 Sodium sulphate 280.0 Zinc sulphate2.5

causing the thread to travel in said bath for a distance not in excessof 25 centimeters, with- Grams per liter Sulphuric acid .i 160.0

Sodium sulphate 250.0 Zinc sulphate 2.5

causing the thread to travel in said bath for a distance not in excessof 25 centimeters, withdrawing the thread from said bath and causing itto travel in the air for a distance of not less than 150 centimeters.

RENE PICARD. RENE FAYS.

